yes, the client calling your api, must set their timeout (typically 60/90 seconds). you only control the server request timeout, and server initiated api calls.
if you are using the aspnetcore hosting module, you configure its request timeout in the webconfig. If using kestrel it has it own setting in the appsetting.json, or startup configuration.
a 100 seconds seems too long. maybe it should be broken into a start request and check status calls.